I agree with Velo on this. 650c may have some advantages for accel, and its common in triathlon [can someone please explain WHY?] but the whole point of a TT is to achieve and maintain a very high speed consistently over a set distance [usually 40 km]. Once you're up to speed, maintaining it will be somewhat easier with the larger wheels.

when walking, just walk. when sitting, just sit. when riding, just ride. above all, don't wobble.

I raced the same TT. Same course and conditions. I did one on 650's and the other on 700's. No real difference. In tri's it is a different story due to the transistions. Most everyone I know that do alot of TT's have gone back to the 700. I'm using a Cervelo and have been very happy with it.
Good Luck & Happy Rides!